Similar incidents grounded flights at another airport in the London area, Gatwick, just before Christmas.

A British Airways plane passes the control tower at Heathrow Airport on April 13, 2012.Steve Parsons / Press Association via AP file

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Jan. 8, 2019, 6:42 PM GMT

By David K. Li

Departures from London's Heathrow Airport, one of the world's busiest, were halted for more than an hour Tuesday after a drone was spotted flying nearby, officials said.

"We are responding to a drone sighting at Heathrow and are working closely with the Met Police to prevent any threat to operational safety," the airport tweeted at 12:47 p.m. ET (5:47 p.m in London).

We are responding to a drone sighting at Heathrow and are working closely with the Met Police to prevent any threat to operational safety. As a precautionary measure, we have stopped departures while we investigate. We apologise to passengers for any inconvenience this may cause.

"As a precautionary measure, we have stopped departures while we investigate," the post continued.

About an hour later, airport officials announced that departing flights had been resumed.

A BBC cameraman, Martin Roberts, just happened to be driving past Heathrow at 5:45 p.m. London time and insisted he saw a drone.

"I could see, I'd say around 300 feet up, very bright, stationary flashing red and green lights," he said in a BBC report. "I could tell it was a drone — these things have got quite distinctive lights — not a helicopter."

The drone lingered in place for several minutes, Roberts told the BBC.

"The lights were very close together. It was a very clear night and the object was stationary. It was turning very, very slightly," he said. "I could see it very clearly, I'd say for about four to five minutes."

Heathrow is the world's fifth-busiest airport, with 78 million passengers in 2017, according to the industry newsletter Airport Technology. The busiest airport is Hartsfield-Jackson Atlanta International, the journal said.